Unilever scientists, in collaboration with scientists at the University of Nottingham, used radioactive labelling of the carbon in octanoic acid added to sunflower oil which was subsequently encapsulated by alginate. This allowed them to measure the digestion of fats as labelled carbon dioxide (13CO2) was produced in the breath during digestion.
The alginate gel matrix was found to delay peak level 13CO2 in the breath of the volunteers by approximately 50 minutes, compared with un-encapsulated labelled sunflower oil.
In addition, magnetic resonance imaging (MRI) was also employed to study how the particles behaved in the gastrointestinal tract of the 11 volunteers who consumed the test foods.
“This study showed that encapsulation is an effective strategy to control the GI fate of lipids,” wrote researchers in the journal Food Hydrocolloids.
“It also showed that multimodal studies including MRI are powerful tools for investigating how the body handles food components and may aid in the design of food products with controlled functionality,” they added.
Obesity implications
The research has important implications for the formulation of foods with weight management potential: a segment of increasing interest from the food interest due to ballooning obesity rates around the world.
“The lipids in food provides mouth-feel and texture which appeals to the consumer, but modulation of lipid absorption, by altering lipid delivery to its main site of digestion and absorption in the small intestine, can provide the opportunity to generate foods with proven health benefits such as prolonged satiety and delayed nutrient absorption,” explained
In effect, the encapsulation acts, not as a fat blocker, but a controlled release system for fat digestion. Proof of this was observed by measuring levels of the gut satiety hormone cholecystokinin (CCK). CCK levels rose quicker for the un-encapsulated sunflower oil, showing that the lipid in the encapsulated form was “not available for immediate digestion due to the alginate bead encapsulation which changed the lipid bioaccessibility”. However, no differences in satiety scores were observed between the groups.
Encapsulation science
Using food grade sodium alginate (ISP Alginates, U.K), the researcher encapsulated 13C labelled octanoic acid and added this to sunflower oil using an Inotech Encapsulator. Un-encapsulated labelled sunflower oil was also prepared.
Eleven volunteers with a mean age of 28 and a mean BMI of 23.0 kg/m2 consumed test meals with encapsulated or un-encapsulated oil. Results showed that the production of labelled CO2 was delayed by an average of 47 minutes following consumption of the encapsulated oil, compared to the control meal with freely available sunflower oil, said the researchers.
MRI data showed the presence of the alginate beads in the lower parts of the bowel. “This suggests that not all the alginate beads are immediately broken down by the intestinal secretions and some remained intact throughout the experiment so that at later time points, some of the lipid only images showed a small number of discrete ‘dots’ of lipid in the ascending colon,” explained the researchers.
“This visualisation data of the beads in the small bowel has important implications for the encapsulation process itself, as a lack of beads visible in the intestine would suggest that the beads broke down rapidly and would not delay the release of lipid, conversely a large number of beads visible in the terminal ileum would suggest that the beads were not broken down easily enough and were retaining the lipid into the ascending colon,” they added.
“Alginate encapsulation is a potential method of manipulating the profile of lipid absorption in healthy subjects,” concluded the researchers.
Source: Food Hydrocolloids
Published online ahead of print, doi: 10.1016/j.foodhyd.2010.11.006
“Encapsulation of lipid by alginate beads reduces bio-accessibility: An in vivo 13C breath test and MRI study”
Authors: C. Hoad, P. Rayment, V. Risse, E. Cox, E. Ciampi, S. Pregent, L. Marciani, M. Butler, R. Spiller, P. Gowland